It's definitely not a case of one size fits all and you may need to experiment to find what suits you best.
But having lost 2 stone over the course of a year, I would offer the following advice;
Dont try to rush it. Its a bit of a cliche but sustaining any weight loss is about changing your lifestyle/habits.
Dont try to totally elliminate a particular food type, e.g. bread , as it will just feel like you are punishing yourself and when you give in you will feel like you have failed.
Also if you cut out any of the key food groups you may become deficient in certain minerals/nutrients/vitamins and this will upset the finely tuned balance of your hormones/body functions etc. The net result will probably be that you will not be able to sustain the diet.
As stated above, cutback on processed/sugary/high GI foods and eat things that are more sustaining, e.g. porridge for breakfast etc. This will make you feel full for longer and suppress the need for snacking between meals. If you need to snack, go for nuts/seeds etc. I also found dark chocolate really useful in the early stages. It gives you that "sugar hit" but is not moorish like dairy chocolate so one or two squares is normally enough.
I ended up spreading my meals throughout the day, rather than having 2 or 3 big meals and then getting big dips in energy/blood sugar in between. I appreciate that that is not easy with a busy job, but with a bit of forward planning (i.e. taking food to work with you) it is achievable.
Make sure your diet is varied and interesting, that way you will get all the minerals/vitamins etc that you need but it will also be enjoyable to eat.
I ended up going low carb and making sure that I didnt eat "white carbs" after lunchtime. Hence my biggest meal of the day is lunch (as that is when I need most of my food intake) and not before I am about to go to bed.
I also dont believe that you should cut out dairy/fat. Just be sensible. Your body needs some fat to function and natural yoghurt is very good for the gut.
Overall the key is a varied but healthy diet combined with exercise. Common sense really.
Going back to your original question about getting "bike fit", whilst you appear to be able to fit in quite a variety of exercise in your busy schedule, you only get out on the bike once a week. Goes without saying that you need to probably spend less time in the gym/swimming and more time on the bike.
If that is not possible, try spinning classes. I recently started spinning twice a week and I really notice the difference when I'm out on my bike.
Like one of the other posters, I also kept a diary and found it a really useful monitoring/planning tool.